In any fluid that is removed through a well or other means from a subterranean reservoir, there will be a certain amount of solid materials carried along in the fluid flow. In the instance of a well which terminates at its lower end in a liquid pool such as water, the amount of solid material will be limited.
In the instance, however, of a hydrocarbon producing well, the latter doesn't usually terminate in a pool but rather in a hydrocarbon bearing substrate. The substrate normally comprises a subterranean formation which will include an agglomerate of materials such as sands, clays, etc.
The in situ pressures in a subterranean reservoir are a function of the depth of the overburden, as well as with the amount of trapped gas present. Nonetheless, the hydrocarbon content of the reservoir will be held in the pores of the earthen material until released and passed to the surface.
Operationally, the hydrocarbons will be urged by underground pressure, toward a perforated well casing in the overburden which represents a low pressure area. From there, the hydrocarbon is urged to the well head and produced in the normal manner.
The hydrocarbon outflow will normally comprise liquid crude oil together with gas, or even gas alone. As a matter of practicality, the two components are separated at the surface. The gas can be either retained for use, or disposed of by flaring. The liquid however, together with any solid materials which it may be carrying is further processed.
Certain forms of substrate will be more amenable to erosion by movement of the hydrocarbon element therethrough than will other types of substrate. In the instance of a primarily sandy environment which embodies largely unconsolidated sand, the latter will be readily carried along in the fluid flow.
The capability for solid particles being carried along with the passing hydrocarbon or gas flow is dependent to a large measure on a number of factors. It relies for example on gas pressure, velocity of the hydrocarbon or gas at its entry into the well, and also on the size distribution of the solid particles in the formation.
Some of the particles are sufficiently small to be carried to the well head and will thereafter be separated from the hydrocarbon stream. This is generally done by a settling system, by gravity, or by similar means. Other sand particles which are too large to be transported by the hydrocarbon stream will remain underground.
In some instances, flow of the sand laden hydrocarbon will result in sand particles being deposited along the normal path of the fluid. For example, the particles can be caught and retained within the many passages, joints and connections encountered between the well casing lower end and the well head.
To obviate this impeding or clogging of a well's passages, means is often provided to physically block movement of the solids. This however must be achieved while permitting only the liquid to pass through. One such means includes the usual well gravel pack, or even filters of various sizes and structure which are positioned within the wall whereby to enhance a continuous filtering operation.
Various forms of sand filters are known in the prior art and have been utilized with a degree of success depending on the conditions of the environment from which the hydrocarbon fluid is extracted.
Toward overcoming or at least alleviating the problem of sand accumulation within a subterranean well, there is presently provided a durable filtering means. The latter is comprised primarily of an elongated casing including an outer member, whose walls are perforated to permit the inward passage of a fluid such as a crude oil or a gas.
The inwardly moving fluid is directed through a filter bed comprised of a metallic mass which defines a multitudinous number of passages therethrough. The metallic mass in one embodiment comprises a generally annular configuration formed of a compressed wool-like media which is retained in a desired shape and density by a surrounding sheath. The filter bed is positioned within an annular filter chamber which extends substantially longitudinally of the filter body.
It is therefore an object of the invention to provide a filter which is capable of segregating out the solid component of a fluid flow. A further object is to provide a filter of the type contemplated wherein a bed comprised of randomly disposed fibrous members defines a plurality of passages which are capable of retaining solid particles therein and for passing the particle-free fluid therethrough. A still further object of the invention is to provide a filter element which is capable of functioning in an elevated temperature environment by separating particulate matter from a fluidic medium. Usually said matter is carried in such manner as to permit it to be physically retained and accumulated.